Promoting NIR-Driven Luminescence Activity of Calcium zinc galliumate via Energy Transfer from Mn⁴⁺ to Ho³⁺ for Second Biological Window

NIR luminescent materials are widely available for biological applications, and the NIR emitting of Ho3+ ions has received widespread attention in the second biological window. In this work, Ca14Zn6Ga10O35 : Mn4+,Ho3+ luminescent materials were synthesized using a high temperature solid state method. Optical properties and energy transfer mechanisms have studied in detail. Upon UV-vis light excitation, the Mn single doped Ca14Zn6Ga10O35 phosphors exhibit deep red and NIR emission centered at 712 and 1151 nm assigned to Mn4+ and Mn5+, respectively. Another stronger NIR emitting peaked at 1195 nm occurs when the Ho3+ ion is co-doped into Ca14Zn6Ga10O35 : Mn4+. The energy transfer from Mn4+ to Ho3+ ion is performed through a resonant type by a dipole-dipole interaction mechanism. In addition, the thermal stability of Ca14Zn6Ga10O35 : Mn4+,Ho3+ phosphor has been investigated, and the NIR emission of Ho3+ ion maintains more than half the strength at 423 K. The findings indicate that the as-prepared Ca14Zn6Ga10O35 : Mn4+,Ho3+ luminescent materials hold promise for potential applications in the second biological window.